Phylogenetic Relationships Within the Genus Equus and the Evolution of α and θ Globin Genes

Sequences of the α1, α2 and θ globin genes from six equid species have been determined to investigate relationships within the genus Equus. Analyses using standard phylogenetic methods, or an approach designed to account for the effects of gene conversion between the α genes, gave broadly similar results and show that the horses diverged from the zebra/ass ancestor ∼2.4 million years ago and that the zebra and ass species arose in a rapid radiation ∼0.9 million years ago. These results from the α genes are corroborated by θ gene data and are in contrast to mitochondrial DNA studies of the phylogeny of this genus, which suggest a more gradual set of speciation events. Received: 22 April 1997 / Accepted: 20 July 1998